Electric rotating machine and stator for the same

ABSTRACT

Disclosed is an electric rotating machine comprising a rotor having N and S poles, a stator including an annular stator core and slots, and multiple-phase stator windings embedded in the slots; wherein the stator windings are formed by winding continuous wires such that straight parts of the stator windings pressed in a flat shape are wound in rings around a cylindrical member provided with grooves. The cylindrical member is inserted into a bore defined by the annular stator core so that the grooves of the cylindrical member are arranged opposite to the slots. The sets of the windings are folded back alternately outside the slots of the stator core and are wound such that the sets of the windings are embedded alternately in the direction of the depth of the slots. Leading and trailing ends of the continuous wires are superposed after being wound at least one turn around the circumferentially arranged slots of the stator.

CLAIM OF PRIORITY

[0001] The present application claims priority from Japanese applicationserial No. 2003-110978, filed on Apr. 16, 2003, the content of which ishereby incorporated by reference into this application.

[0002] 1. Technical Field of the Invention

[0003] The present invention relates to an electric rotating machineand, more particularly, to a stator included in the electric rotatingmachine, such as a generator for vehicles.

[0004] 2. Description of the Prior Art

[0005] In a stator of a conventional automotive alternator disclosed in,for example, Jpn. Pat. No. 2,927,288, stator windings of short lengthconductor segments formed in substantially U-shape are inserted intoslots, wherein the inserted conductor segments are joined at ends of thewindings.

[0006] Whereas the conventional stator employs the conductor segments, astator disclosed in JP-A No. 2001-245446 is formed by inserting straightwindings in slots formed in a straight stator core in the direction ofthe depth of the slots. Then, the straight stator core is shaped bybending into a cylindrical shape at a post processing, thereby toincrease the space factor of the conductor in the slots and to simplifythe method of fabricating the stator.

[0007] Although the space factor of the windings embedded in the slotsincreases remarkably, the stator core cannot be formed in a satisfactoryroundness by rolling the flat stator core after embedding the windingsin the slots, and gaps are formed in the joint of the opposite sides ofthe flat stator core. Consequently, the stator core causes problemsincluding the enhancement of magnetic noise and the reduction of output.Defective insulation of the windings embedded in the slots occurs due todamaging insulating paper and the insulating coatings of the wires ofthe windings embedded in the slots by welding heat applied thereto inwelding the joint in the cylindrical stator core.

[0008] In fabricating the known automotive alternator mentioned in Jpn.Pat. No. 2927288, the plurality of short conductor segments need to befitted in the slots of the stator core and the ends of the conductorsegments need to be bonded by welding or the like. Thus, the automotivealternator requires troublesome assembling work and the insulation ofthe conductors is liable to be damaged. The joined parts are oftenmelted and-short-circuited during welding, and the automotive alternatoris difficult to mass-produce.

[0009] Ends of the coils are joined in a plurality of joints, the jointsare liable to be short-circuited and thereby the coils are oftenshort-circuited. Since the plurality of conductor segments are fitted inthe slots of the stator core, and the ends of the conductor segments arejoined together by welding or the like, troublesome work is needed forpositioning the plurality of ends.

[0010] If the insulating films coating the joining ends of the conductorsegments are removed incompletely, organic gases are produced duringwelding and deteriorate the quality of the joints. Thus, additional workis needed for removing the insulating films.

[0011] When ends of the conductor segments are melted for welding, thejoints are often short-circuited, reducing the quality of mass-producedstators.

[0012] The stator disclosed in JP-A No. 2001-245446 is formed byembedding windings in the slots formed in the flat stator core, rollingthe flat stator core in a cylindrical shape and joining together theopposite sides of the rolled stator core in a butt joint. Thus, thestator core causes problems including the enhancement of magnetic noise,the reduction of output and the defective insulation of the windings.

[0013] Although the space factor of the windings increases remarkably,the stator core cannot be formed in a satisfactory roundness by rollingthe flat stator core after embedment of the windings in the slots, andgaps are formed in the joint of the opposite sides of the flat statorcore. Consequently, the stator core causes problems including theenhancement of magnetic noise and the reduction of output. Defectiveinsulation of the windings embedded in the slots occurs due to damaginginsulating paper and the insulating coatings of the wires of thewindings embedded in the slots by welding heat applied thereto inwelding the joint in the cylindrical stator core.

SUMMARY OF THE INVENTION

[0014] The present invention is intended to solve those problems and itis therefore an object of the present invention to provide a stator foran electric rotating machine, capable of being efficiently assembled,and provided with windings less subject to short circuit and mounted ona stator core in a satisfactorily insulated state.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015]FIG. 1 is a sectional view of an automotive alternator in a firstembodiment according to the present invention.

[0016]FIG. 2 is a perspective view of a stator included in theautomotive alternator shown in FIG. 1.

[0017]FIG. 3 is a perspective view of a stator core shown in FIG. 1.

[0018]FIG. 4 is a view of assistance in explaining a procedure forforming windings.

[0019]FIG. 5 is a view of assistance in explaining a procedure forforming a flat winding set.

[0020]FIG. 6 is a plan view of a flat winding set.

[0021]FIG. 7 is a view of assistance in explaining a procedure forrolling a flat winding set in an annular shape.

[0022]FIG. 8 is a sectional view of assistance in explaining a procedurefor inserting an annular winding set in a stator core.

[0023]FIG. 9 is a view of assistance in explaining a procedure forinserting an annular winding set in a stator core.

[0024]FIG. 10 is a sectional view of assistance in explaining the stateof conductors in a slot.

[0025]FIG. 11 is a perspective view of a stator included in a secondembodiment according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0026] To solve the problems the present invention forms stator windingsfor a stator included in an electric rotating machine by winding aplurality of continuous wires around a spool, forms flat straight partsof the stator windings to be embedded in the slots of the stator core bypress-forming straight parts of the stator windings, winds a statorwinding set in an annular shape around a cylindrical member providedwith grooves the number of which is equal to that of the slots of thestator core, inserts the cylindrical member in a bore defined by theannular stator core, adjusts the position of the cylindrical member inthe bore of the annular stator core so that the grooves of thecylindrical member are positioned opposite to the slots of the statorcore, respectively, expands and inserts the straight parts of thewindings wound around the grooves in the slots of the stator core in anexpanded manner, folds back the winding set alternately outside theslots of the stator core to form windings embedded alternately in thedirection of the depth of the slots every predetermined number of slots,and winds leading and trailing ends of the plurality of continuous wiresat least one turn around the circumferentially arranged slots of thestator core so that the leading and the trailing ends of the pluralitycontinuous wires are superposed.

[0027] In the stator of the electric rotating machine according to thepresent invention, the stator windings are formed in at least twowinding sets by winding a plurality of continuous wires, and the statorwindings are arranged at intervals of the predetermined number of slotsso that the trailing ends of the winding sets may not be superposed withrespect to a circumferential direction of the stator core.

[0028] In the stator of the electric rotating machine according to thepresent invention, the slots of the stator core are open slots.

[0029] In the stator of the electric rotating machine according to thepresent invention, the stator windings embedded in the slots of thestator core are fixed in place by driving magnetic wedges in the slots.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0030] Rotors for electric rotating machines in preferred embodimentsaccording to the present invention will be described with reference tothe accompanying drawings.

First Embodiment

[0031]FIG. 1 is a sectional view of an automotive alternator in a firstembodiment according to the present invention, FIG. 2 is a perspectiveview of a stator included in the automotive alternator shown in FIG. 1,and FIG. 3 is a perspective view of a stator core shown in FIG. 1.

[0032] The alternator includes a case 3 having an aluminum front bracket1 and an aluminum rear bracket 2, a shaft 5 extended in the case 3 andhaving one end part on which a pulley 4 is fixedly mounted, a Randalltype rotor 6 fixed to the shaft 5, fans 7 attached to the opposite endsurfaces of the rotor 6, a stator 8 fixed to the inside surface of thecase 3, a slip ring fixed to the other end part of the shaft 5 to supplycurrents to the rotor 6, a pair of brushes 10 in sliding contact withthe slip ring 9, a brush holder 11 internally holding the brushes 10, arectifier, not shown, electrically connected to the stator 8 to convertan alternating current generated in the stator 8 into a direct current,and a voltage regulator, not shown, for regulating ac voltage generatedin the stator 8.

[0033] The rotor 6 includes rotor coils 12 through which a current flowsto generate magnetic flux, and a pair of pole cores 13 and 14 coveringthe rotor coils 12. The pair of pole cores 13 and 14 is formed of ironand is provided with claw-shaped magnetic pole pieces circumferentiallyarranged at equal angular intervals on their circumferences. The polecores 13 and 14 are disposed opposite to each other and the shaft 5 ispressed in the bores of the pole cores 13 and 14 so that the magneticcores are engaged.

[0034] The stator 8 has a laminated stator core 16 provided in its innercircumference with axial slots 15 arranged at predetermined angularintervals, multiple-phase stator windings 17 held on the stator core 16,and insulating members 18, such as insulating paper sheets, inserted inthe slots 15 to insulate the multiple-phase windings 17 electricallyfrom the stator core 16. Each of the multiple-phase windings 17 isformed in a wave winding in the slots 15 by folding back a singleconductor 19 at the axial ends of the stator core 16 so as to form aninner and an outer layer alternately with respect to the depth of theslot 15 every predetermined number of slots 15. In this embodiment, thestator core 16 is provided with ninety-six slots 15 arranged at equalangular intervals to hold one set of multiple stator windings 20(three-phase stator windings) for the sixteen magnetic poles of therotor 6. The conductor 19 is a long, insulated copper wire having arectangular cross section. The stator 8 thus constructed will bedescribed. FIGS. 4 to 11 are views of assistance in explaining a windingset fabricating procedure for forming a winding set forming the statorwindings.

[0035] Referring to FIG. 4, twelve long conductors 19 are wound parallelto each other on a spool 21. The spool 21 has four members, namely, apair of winding members 22 and 23 corresponding to straight parts of theslots of the stator, and a pair of winding members 24 and 25corresponding to the coil ends of the stator. The spool 21 has a shaperesembling a hexagonal cylinder. Grooves for guiding the conductors 9are formed in the surfaces of the winding members 22 and 23 at pitchesequal to those of the stator slots. The depth of the grooves is lessthan half the diameter of the conductors 19.

[0036] Referring to FIG. 5, the spool 21 is held between forming members26 and 27. Guide grooves similar to those of the members 22 and 23 areformed in part of the forming members 26 and 27. Then, the windingmembers 22 and 23 are shifted toward each other with the conductors 19wound on the spool 21 partly received in the grooves of the formingmembers 26 and 27 to release the conductors 19 from the winding members22 and 23, and the winding members 22 and 23 are extracted in thedirection of the axis of the spool 21. Likewise, the winding members 24and 25 are extracted from the wound conductor 19 in the direction of theaxis of the spool 21. Then, the forming members 26 and 27 holding theconductors 19 in their grooves are moved toward each other to form aflat winding set 28 of the conductors 19 as shown in FIG. 6 byflattening the windings of the conductors 19.

[0037] Then, as shown in FIG. 7, the winding set 28 with the conductors19 received in the grooves of the forming member 27-is wound around aninserting jig 29 such that the conductors 19 are received in grooves 30formed in the circumference of the inserting jig 29. The forming member27 is formed of a flexible material, such as silicone rubber. Thediameter of the inserting jig 29 is slightly smaller than the insidediameter of the stator core 16. The pitches of the grooves 30 of theinserting jig 29 are equal to those of the-stator slots. In thisembodiment, the depth of the grooves 30 is not less than twice thediameter of the conductor 19.

[0038] Referring to FIG. 8, cup-shaped retaining jigs 31 and 32 are puton the opposite coil end parts of the winding set 28 wound around theinserting jig 29. The retaining jig 31 is provided with a recess toprovide a clearance for the end part of the winding set 28. The outsidediameters of the retaining jigs 31 and 32 are equal to the diameter ofthe inserting jig 29. Then, the inserting jig 29, the winding set 28 andthe retaining jigs 31 and 32 are united integrally in an assembly, andthe assembly is inserted axially in a bore defined by the stator core16. When the assembly is thus inserted in the stator core 16, thepositional relation between the assembly and the stator core 16 isadjusted so that the grooves 30 of the inserting jig 29 correspond tothe slots of the stator core 16, respectively. The insulating members 18are fitted beforehand in the slots.

[0039] Referring to FIG. 9, the retaining jigs 31 and 32 are removed,and the winding set 28 is expanded and pressed in the slots withexpanding jigs 33 and 34 and, at the same time, the coil end parts arepressed axially with pressing jigs 35 and 36. Consequently, the pitchesof parts, to be fitted in the slots, of the conductors 19 of the windingset 28 are increased to facilitate pressing the conductors 19 in theslots. The slots are open slots and hence the conductors 19 can be thuseasily pressed in the slots.

[0040] Referring to FIG. 10, conductors 19 for two turns are fitted ineach of the stator slots 37. A wedge 38 is fixedly driven in an innerend part of the slot 37 to prevent the conductors 19 from coming offradially inward from the slot 37. Desirably, the wedge 38 is a magneticwedge formed of a magnetic material to reduce loss in a magnetic circuitattributable to open slots.

[0041] The expanding jigs 33 and 34, the pressing jigs 35 and 36, andthe inserting jig 29 are removed, and the ends of the conductors 19 areconnected to form multiple stator windings 20. An insulating resin isapplied to the assembly of the stator core 16 and the winding set 28 toconnect the conductors 19 together, and to fix the conductors 19 to andinsulate the same from the stator core 16. Thus, the stator 8 iscompleted. Prepreg sheets impregnated with an insulating resin may beused as the insulating members 18 inserted in the slots 37 and thewedges 38 instead of the insulating resin.

[0042] The multiple-phase windings 20 of this automotive alternator areformed by using the twelve continuous conductors 19 and hence work forinserting a plurality of short conductor segments in a stator core andconnecting end parts by welding or the like is not necessary. Thus, thestator can be very efficiently manufactured. Since the flat winding set28 is rolled in a cylinder and the rolled winding set 28 is inserted inthe annular stator core 16, the efficiency of assembling work forassembling the stator is very high as compared with prior art assemblingwork that inserts a plurality of conductor segments one by one in slots.Since bent parts 39 of the conductors 19 form the coil ends, joints inthe coil end parts appear only at joints of the respective ends of theleading and the trailing end of the winding set 28 and joints ofconnecting wires. Thus, the stator 8 has a very small number of joints.Consequently, the breakage of the insulating films that is caused byforming the joints and the resultant short-circuit failures can becontrolled, and hence the stator is excellently insulated.

[0043] Since the stator core 16 is a unitary annular member, is notformed by rolling a flat member and does not have any butt joint,magnetic noise can be reduced, and faulty insulation attributable tobutt welding can be prevented.

[0044] Since the conductors 19 have a rectangular cross section, thesectional shape of the straight parts fitted in the slots 37 conforms tothe shape of the slot 37. Thus, the conductors 19 can be satisfactorilyfitted in the slots 37 in a high space factor, and heat can beefficiently transferred from the conductors 19 to the stator core 16.

Second Embodiment

[0045]FIG. 11 shows a second embodiment of the present invention. Afirst winding set 28 and a second winding set 40 are mounted in thatorder on a stator core 16 by the same procedure as that employed in thefirst embodiment. The ends 42 of the conductors forming the secondwinding set 40 are spaced a predetermined number of slots (e.g., 12×nslots) from the ends 41 of the conductors forming the first winding set28 on the stator core 16. Thus, the number of the conductors of thesecond embodiment is twice that of the conductors of the firstembodiment, and hence the output of the second embodiment is higher thanthat of the first embodiment. Since the ends of the conductors of thefirst winding set are spaced a predetermined number of slots (e.g., 12×nslots) from the ends of the first winding set, the possibility of shortcircuit that occurs in connecting the ends of the conductors and theconnecting wires can be reduced. Since the same assembling jigs are usedfor mounting both the first winding set 28 and the second winding set 40on the stator core 16, the cost of jigs can be reduced.

[0046] The alternator according to the embodiments of the presentinvention has the multiple-phase stator windings formed by winding thecontinuous conductors, and the method of fabricating the alternatoraccording to the present invention forms the multiple-phase statorwindings by winding the continuous conductors. Therefore, a processneeded by the prior art stator for inserting a plurality of conductorsegments in slots formed in a stator core, and a process for connectingthe ends of the conductor segments are unnecessary. Thus, the stator ofthe electric rotating machine according to the present inventionfacilitates assembling work. The remarkable reduction of joints reducesshort-circuit failures attributable to the formation of joints, andimproves quality. Since the stator core is a unitary annular member, theincrease of magnetic noise and faulty insulation attributable to rollinga flat member and butt welding opposite sides of the rolled flat membercan be prevented.

[0047] According to the alternator and the method of fabricating thesame of the embodiments of the present invention, output can beincreased because an increased number of conductors can be embedded ineach of the slots of the stator core. Since the ends of the conductorsare distributed, the possibility of short-circuit failures attributableto work for connecting the ends of the conductors and the connectingwires can be reduced.

[0048] According to the alternator and the method of fabricating thesame of the embodiments of the present invention, the conductors can beefficiently fitted in the slots, and damaging the insulation of theconductors by the edges of the slots can be prevented.

[0049] According to the alternator and the method of fabricating thesame of the embodiments of the present invention, magnetic circuit lossattributable to open slots can be controlled.

1. An electric rotating machine comprising: a rotor having a pluralityof N and S poles alternately arranged in a rotating direction; a statorincluding an annular stator core surrounding the rotor and provided witha plurality of slots, and multiple-phase stator windings embedded in theslots; and a frame supporting the rotor and the stator; wherein thestator windings are formed by winding a plurality of continuous wiresaround a spool such that straight parts of the stator windings pressedin a flat shape are wound in rings around a cylindrical member providedwith grooves the number of which is equal to that of the slots, thecylindrical member is inserted in a bore defined by the annular statorcore so that the grooves of the cylindrical member are arranged oppositeto the slots, respectively, sets of the windings are folded backalternately outside the slots of the stator core and are wound such thatthe sets of the windings are embedded alternately in the direction ofthe depth of the slots every predetermined number of slots, leading andtrailing ends of the plurality of continuous wires are superposed afterbeing wound at least one turn around the circumferentially arrangedslots of the stator.
 2. The electric rotating machine according to claim1, wherein the stator windings are at least two sets of windings formedby winding a plurality of continuous wires, and the stator windings arearranged with displacement of a predetermined number of slots so thatthe trailing ends of the sets of windings may not be superposed withrespect to a circumferential direction of the stator core.
 3. Theelectric rotating machine according to claim 1, wherein the slots of thestator core are open slots.
 4. The electric rotating machine accordingto claim 3, wherein the stator windings embedded in the slots of thestator core are fixed in place by inserting magnetic wedges in theslots.
 5. A method of fabricating an electric rotating machine includinga rotor having a plurality of N and S poles alternately arranged in arotating direction, a stator including an annular stator coresurrounding the rotor and provided with a plurality of slots, and amultiple-phase stator windings embedded in the slots, and a framesupporting the rotor and the stator, said method comprising; forming thestator windings by winding a plurality of continuous wires around aspool; press-forming flat straight parts of the stator windings to beembedded in the slots of the stator core; winding a stator winding setin the annular shape around a cylindrical member provided with groovesthe number of which is equal to that of the slots of the stator core;inserting the cylindrical member in a bore defined by the annular statorcore; adjusting the position of the cylindrical member in the bore ofthe annular stator core so that the grooves of the cylindrical memberare positioned opposite to the slots of the stator core, respectively;expanding and inserting the straight parts of the windings wound aroundthe grooves in the slots of the stator core; alternately folding backthe winding set outside the slots of the stator core to form windingsembedded alternately in the direction of the depth of the slots everypredetermined number of slots; and winding leading and trailing ends ofthe plurality of continuous wires at least one turn around thecircumferentially arranged slots of the stator core so that the leadingand the trailing ends of the plurality continuous wires are superposed.6. The method according to claim 5, wherein the stator windings areformed in at least two winding sets by winding a plurality of continuouswires, and the stator windings are arranged at intervals of apredetermined number of slots so that the trailing ends of the sets ofwindings may not be superposed with respect to a circumferentialdirection of the stator core.
 7. The method according to claim 5,wherein the slots of the stator core are open slots.
 8. The methodaccording to claim 7, wherein the stator windings embedded in the slotsof the stator core are fixed in place by inserting magnetic wedges inthe slots.
 9. A plurality of stator windings embedded in a plurality ofslots formed in a stator core surrounding a rotor provided withalternate N and S magnetic poles, supported on a frame and included inan electric rotating machine, said stator windings being formed by amethod comprising the steps of: winding a plurality of continuous wiresaround a spool; winding flat straight parts of the stator windings to bepress-formed in flat straight parts in rings around a cylindrical memberprovided with grooves the number of which is equal to that of the slotsof the stator core; inserting the cylindrical member in a bore definedby the annular stator core; adjusting the position of the cylindricalmember in the bore of the annular stator core so that the grooves of thecylindrical member are positioned opposite to the slots of the statorcore, respectively; alternately folding back the sets of the windingsoutside the slots of the stator core to form windings embeddedalternately in the direction of depth of the slots every predeterminednumber of slots; and winding leading and trailing ends of the pluralityof continuous wires at least one turn around the circumferentiallyarranged slots of the stator core so that the leading and the trailingends of the plurality continuous wires are superposed.
 10. The statorwindings according to claim 9, wherein the stator windings are formed inat least two winding sets by winding a plurality of continuous wires,and the stator windings are arranged at intervals of a predeterminednumber of slots so that the trailing ends of the winding sets may not besuperposed with respect to a circumferential direction of the statorcore.
 11. The stator windings according to claim 9, wherein the slots ofthe stator core are open slots, and the stator windings are embedded inthe slots.
 12. The stator windings according to claim 9, wherein thestator windings embedded in the slots of the stator core are fixed inplace by driving magnetic wedges in the slots.
 13. The electric rotatingmachine according to claim 2, wherein the slots of the stator core areopen slots.
 14. The method according to claim 6, wherein the slots ofthe stator core are open slots.